During the twentieth century, most farmers began to heavily cultivate their land to increase crop yields. After the fall harvest, a farmer often plowed under the entire field from fence post to fence post. Fertilizer would often be applied over the entire field at the same time. Again, before the spring planting, the farmer would retill the field and apply more fertilizer to further prepare the soil for planting.
While this full field tillage method of farming does produce large crops, it does so at a substantial economic and environmental cost. It is expensive to fertilize large fields due to the need to purchase and spray large quantities of fertilizer. Moreover, fertilizer will wash or run off a farm field and enter nearby waterways such as creeks, rivers, lakes and the like. Such fertilizer then becomes a pollutant, degrading water quality and promoting the growth of unhealthy vegetation, such as algae, in the waterway.
In addition, plowing an entire field under exposes the soil to the elements. Wind and water act on the exposed soil and can blow or wash away large quantities of valuable and irreplaceable soil. The crop residue left after a harvest, namely the unremoved crop stubble and crop remnants, normally anchor the soil against the erosion caused by wind and water. However, in the full field tillage method of farming under consideration, this crop residue has been plowed under and is no longer effective to prevent erosion. Erosion of agricultural fields is a serious problem which could limit future food production by making the land less productive.
Alternative methods of farming have been proposed to try and solve some of the problems noted above. For example, in no till farming, the field is not plowed under after harvest, but is left in an untilled state with crop residue covering the field. This crop residue is effective in limiting soil erosion. However, crop yields are generally not as high with no till farming as with full field tillage. In addition, some farmers may have aesthetic objections to a no till field when compared to a plowed field. Thus, no till farming has had limited use by farmers despite its environmental advantages.
Strip tillage or zone tillage are synonymous terms and refer to a method of farming for crops that grow in rows, such as corn or soybeans. In zone tillage, the farmer does not till and fertilize the entire field, but only the elongated strips or zones of ground that will be planted with the upcoming season's row crop. Moreover, the farmer uses a less aggressive tilling method and does not completely plow or turn the soil under.
Row crops have variable row spacing depending upon the crop being planted, the characteristics of an individual farmer's land and the farmer's own preferences. The spacing may range from 15″ to 40″ or more. For example, corn is often planted in rows that are 30″ apart. Zone tillage tills a zone for each crop row that is only a few inches to a foot or so wide leaving the remaining ground between adjacent rows completely untilled. The crop residue left in the untilled ground acts to prevent or limit soil erosion.
In addition, zone tillage is far more economical in the use of energy and fertilizer than when the entire field is plowed under and fertilized. Only approximately one third of the field is tilled and fertilized in zone tillage. Fuel consumption and wear and tear on a farmer's equipment are reduced. In addition, the cost for fertilizer is significantly lowered since only one third to one half of the previous amounts of fertilizer are now used. Nonetheless, weed growth is significantly retarded since weed seeds in the untilled ground between adjacent zones remain undisturbed and since no fertilizer is applied to such untilled ground, thereby preventing or slowing the germination of the weed seeds and the growth of weeds.
Farming experts consider zone tillage to have the same environmental benefits as no till farming. Yet, unlike no till farming, crop yields do not appear to significantly suffer compared to the yields from more conventional farming methods. In fact, some studies indicate that crop yields from zone tillage may actually surpass the crop yields from full field tillage and fertilization.
Conventionally, zone tillage in the fall involves the use of a tillage coulter to cut a slit in the ground followed by a trailing fixed rear knife or shank having a forwardly facing cutting tooth. This fall tool (i.e. a single coulter with trailing fixed rear knife) has to reach a depth of 6 to 10 inches or so. A pair of containment coulters roll along behind the knife to help confine the soil to the zone that has been tilled, namely to prevent the soil from spreading laterally outside the zone.
In the spring, zone tillage involves just the use of one or more tillage coulters rolling through the zone without the trailing fixed rear knife and without the containment coulters used in the fall. Spring tillage is done at far shallower depths than in the fall, i.e. at depths of 2 to 3 inches.
Known zone tillage tools and methods have certain problems that limit wider adoption of zone tillage by farmers. As one pushes a knife forwardly through the ground, it is common for some of the crop residue in the zone being tilled to catch or snag around the knife and trail rearwardly from the knife. This is a condition known as plugging. When too much residue or debris plug the knife, the farmer must stop and clear the residue or debris by hand. This is obviously inconvenient and time consuming.
Moreover, zone tillage has to date been best suited for use on relatively flat ground. When zone tillage has been tried on sloping ground, there has been a tendency for washouts to occur. This is where rainwater runs down the tilled zones in a field and washes some of the loosened soil out of the zones by carrying the soil along the zones down the slope of the hill.
Thus, there is a need in the farming art for a new method of zone tillage as well as a new tool for solving some of these problems. This invention provides such a new method and new tool of zone tillage.